rb_env_t may use a flexible array, helps a little even on my busy system:

http://80x24.org/misc/m/1410173063-19208-1-git-send-email-e%4080x24.org.txt

trunk   135.18708946416155
trunk   123.50244501209818
trunk   133.2718793260865
fa      109.13581056008115
fa      116.52121020900086
fa      114.37961085699499

-----------------------------------------------------------
raw data:

[["app_lc_fizzbuzz",
  [[135.18708946416155, 123.50244501209818, 133.2718793260865],
   [109.13581056008115, 116.52121020900086, 114.37961085699499]]]]

Elapsed time: 732.008122514 (sec)
-----------------------------------------------------------
benchmark results:
minimum results in each 3 measurements.
Execution time (sec)
name    trunk   fa
app_lc_fizzbuzz 123.502 109.136

Speedup ratio: compare with the result of `trunk' (greater is better)
name    fa
app_lc_fizzbuzz 1.132